Data Relay Systems for a Mars Human Base in Meridiani Planum

L. NikulásdóttirT. Velasco

1. Scope2. Requirements for the Communications3. Critical Parameters4. Case by Case Analysis5. Summary6. Optical Communications7. Conclusions

1. Scope

Scope of the Study: • Identify the Requirements and Criticalities for Communications

with the Mars Surface• Analyse the Main options for Mars-Earth Relay Satellite• Identify the best Strategy for a Mars Human Base in Meridiani

Planum Base

Meridiani Planum is located close to the Equator (1.9S; 354.5E)

2. Requirements for the Communications

• Current Systems – not communication satellites• NASA Mission Mars Telecommunications Orbiter (2009)• Demanding Requirements for a Human Mission

Mars Odissey, source: NASA/JPL

Mars Telecommunications Orbiter, source: NASA/JPL

2. Requirements for the Communications

• High Data Volume Communications

• High Data Rate Communications

• “Continuous” Communications - occultations

2. Requirements for the Communications

• Reliability of the System

• Missions Survey

2. Requirements for the Communications

Mission Year / Agency Data Rate to Earth

Mars Global Surveyor 1996 / NASA ~10kbps

Mars Odyssey 2001 / NASA ~14kbps

Mars Express 2003 / ESA ~97kbps

Mars Reconnaissance Orbiter 2005 / NASA ~200kbps

Mars Telecommunications Orbiter 2009 / NASA ~1Mbps

Data rates from Mars orbiting spacecraft to Earth. Values are estimated for the maximum distance Earth to Mars

3. Critical Parameters for Communications

• Data Rates

• Link Visibility Mars Surface to Earth• Link Visibility Mars Surface to Relay Satellite• Link Visibility Relay Satellite to Earth• Technical Feasibility (by 2019) and Costs (v)

• Reliability/Redundancy

KdBJKdBTGdBNEdBLdBmEIRPbpsBR RXrequiredbPROPTX /6.198)/(/)(/)()()( ,0

orbincreq vvv vr

v MARSinc

2

4. Case by Case Analysis

Low Mars Orbit

• Used for MER through Mars Odissey and MGS

• Typically 400km – Polar/Sun-synchronous

• Low Coverage (2%)• Low Data Volume• Constellations increase

performances

4. Case by Case Analysis

Medium Mars Orbit

• Increases coverage time• MTO (2009)• Higher v for insertion

4. Case by Case Analysis

High Elliptical Orbit

• Higher coverage• Continuous communication

possible with two satellites • Low v required for insertion

4. Case by Case Analysis

Areostationary Orbit

• Equivalent to Geostationary orbit for Earth• Continuous coverage of the surface• Two satellites would provide continuous link with Earth• High v required• Needs orbit corrections

4. Case by Case Analysis

Mars Moons

• Use of Phobos or Deimos orbiters• Performances are not very high

4. Case by Case Analysis

Mars Occultation

• The Sun or Moon is between Mars and the Earth

• Occultation by the Moon is short (28 minutes)• Occultation by the Sun can happen each approx. 2 years, and can last

up to 3 weeks• Occultation by the Sun will not occur in 2019 nor 2021

4. Case by Case Analysis

“Trojan” Orbit

• Satellite located in L4 or L5 Earth-Sun Lagrange points

• Not optimal performances, but solves the problem of occultation

4. Case by Case Analysis

Lagrange Points

• Use L1 and L2 Sun-Mars • Good coverage• Low data rates (high

distance from Mars orbit)• High v needed

5. Summary

Orbit Bit Rate Coverage Comments/Pro’s/Con’s

LMO low lowBig Constellation needed/ Low cost / Low performance

MMO high medConstellation needed / better performances / High cost

HEO high med/ high> two S/C needed / Low cost/ Performances are limited

Stationary very high high> two S/C needed / Best performances / Very high cost

Trojans med med For Mars occultations

6. Optical Communications

• Limitation of the RF Systems• Limitation of the Bit Rates – increasing absorption• Laser Communications are the alternative• Technical Challenges: accurate pointing, cloud and dust

attenuation, components, etc• Mars Telecommunications Orbiter – Mars Laser

Communications Demonstration (MLCD)

MTO Laser communications, source: NASA/JPL

7. Conclusions and Recommendations

• High Bit Rate and Continuous Coverage are Mandatory for a Human Mission on Mars

• Constellation of HEO or Areostationary seems to be the best solution. HEO is preferred for the low v needed for insertion

• Further Work to Optimise the Concept (Failure Recovery Modes)

• Development of Optical Communications would be big step forward

The end

or… …The Beginning?